Simulated sunflecks have large, rapid effects on plant stem extension

Abstract

CONTINUOUS simulated shade light quantity¹ and shade light quality² both modulate plant stem extension. However, in nature, shade light is not static, but is invariably, periodically interrupted by sunlight, in a manner primarily dependent on vegetation density and canopy structure^3–5. The significance of ‘sunflecks’ to growth and development of shaded vegetation remains almost unknown. Certainly in etiolated tissue, abnormal changes of light quality have been found to mediate very rapid changes of hypocotylar extension rate⁶, and in green tissue of deeply shaded plants the maintenance of photosynthesis above the compensation point may be highly dependent on light from sunflecks⁵. Furthermore, after very long treatment periods, developmental changes have been observed in response to short term light/dark alternations⁷. We report here that very brief changes of the light environment, simulating sun-flecks, can elicit rapid, marked, changes in extension rate in mature green plants.